Preheat the oven to 350°F (180°C). Line a baking tray with parchment paper.
Working in batches of four, place a couple tablespoons of grated Parmesan onto the baking tray and spread into 3-inch circles, leaving space between each one.
Bake for 4–5 minutes, or until the Parmesan is melted and lightly golden around the edges. Remove from the oven and let sit for about 30 seconds until firm enough to lift with a spatula.
Quickly place each melted Parmesan round over an upside-down muffin tin cavity. Lay a paper towel over the top and gently shape the cheese around the muffin cup to form a bowl. If the cheese hardens too quickly, place it back in the oven for about 1 minute to soften again. Let cool completely before removing. Repeat with remaining Parmesan.
In a medium bowl, toss chopped romaine lettuce with Caesar dressing and diced chicken if using. Add dressing gradually to avoid overdressing the salad.
Fill each Parmesan cup with Caesar salad. Top with pancetta or bacon and croutons before serving.